As a medical image diagnosis apparatus such as an X-ray computed tomography (CT) apparatus, a magnetic resonance imaging (MRI) apparatus, and an ultrasound diagnosis apparatus, an apparatus that can create three-dimensional medical image data (hereinafter, “volume data”) has been in practical use. Such a medical image diagnosis apparatus collects imaging data by taking images of a target object, and generates volume data by performing image processing onto the collected imaging data. Furthermore, the medical image diagnosis apparatus performs volume rendering onto the generated volume data and thereby generates a display image to display on the monitor.
On the other hand, a monitor that allows stereoscopic viewing of a two-viewpoint parallax image taken from two different viewpoints with a special device such as a stereopsis glasses has been brought into practical use. Moreover, a monitor that allows stereoscopic viewing of a multi-viewpoint parallax image taken from multiple viewpoints (e.g., nine-viewpoint parallax image) by use of a light beam controller such as a lenticular lens with the naked eye has also been into practical use. The two-viewpoint parallax image or nine-viewpoint parallax image displayed on a stereoscopic viewing monitor may be generated by estimating the depth information of an image taken from a single viewpoint and performing image processing based on the estimated information.    Patent Literature 1: Japanese Patent Application Laid-open No. 2005-86414